EPA Finds TCE, as a Whole Chemical Substance, Poses an Unreasonable Risk to Human Health

The U.S. Environmental Protection Agency (EPA) announced on January 9, 2023, the availability of the final revision to the risk determination for trichloroethylene (TCE) risk evaluation issued under the Toxic Substances Control Act (TSCA). 88 Fed. Reg. 1222. EPA determined that TCE, as a whole chemical substance, presents an unreasonable risk of injury to human health when evaluated under its conditions of use (COU). EPA states that the revision to the risk determination reflects its announced policy changes to ensure the public is protected from unreasonable risks from chemicals in a way that is supported by science and the law.

In its January 9, 2023, press release, EPA states that TCE is a volatile organic compound (VOC) used mostly in industrial and commercial processes. Consumer uses include cleaning and furniture care products, arts and crafts, spray coatings, and automotive care products like brake cleaners.

In its revised risk determination, EPA found that TCE presents unreasonable risk to the health of workers, occupational non-users (ONU) (workers nearby but not in direct contact with this chemical), consumers, and bystanders. EPA identified risks for adverse human health effects not related to cancer, including neurotoxicity and liver effects, from acute and chronic inhalation and dermal exposures to TCE. EPA also identified risks for cancer from chronic inhalation and dermal exposures to TCE.

EPA states that it used the whole chemical risk determination approach for TCE in part because there are benchmark exceedances for multiple COUs spanning across most aspects of TCE’s life cycle, from manufacturing (including import), processing, commercial use, consumer use, and disposal for health of workers, ONUs, consumers, and bystanders, and because the health effects associated with TCE exposures are “severe and potentially irreversible” (including developmental toxicity, reproductive toxicity, liver toxicity, kidney toxicity, immunotoxicity, neurotoxicity, and cancer).

EPA determined that 52 of the 54 COUs evaluated drive the unreasonable risk determination. Two out of 54 COUs do not drive the unreasonable risk: consumer use of TCE in pepper spray and distribution in commerce. The revised risk determination supersedes the COU-specific no unreasonable risk determinations that EPA previously issued by order under TSCA Section 6(i) in the 2020 TCE risk evaluation.

EPA notes that the revised risk determination for TCE does not reflect an assumption that workers always and appropriately wear personal protective equipment (PPE), even though some facilities might be using PPE as one means to reduce workers’ exposure. EPA states that this decision “should not be viewed as an indication that EPA believes there is widespread non-compliance with applicable Occupational Safety and Health Administration (OSHA) standards.” In fact, according to EPA, it received public comments from industry respondents about occupational safety practices currently in use at their facilities and will consider these comments, as well as other information on use of PPE, engineering controls, and other ways industry protects its workers as potential ways to address unreasonable risk during the risk management process. EPA will consider this information as part of the risk management process.

EPA acknowledges that there could be occupational safety protections in place at some workplace locations. Not assuming use of PPE in its baseline exposure scenarios, however, reflects EPA’s recognition that certain subpopulations of workers exist that may be highly exposed because:

• They are not covered by OSHA standards (e.g., self-employed individuals and public sector workers who are not covered by a state plan);
   
• Their employers are out of compliance with OSHA standards;
   
• OSHA’s chemical-specific permissible exposure limits (PEL) (largely adopted in the 1970s) are described by OSHA as being “outdated and inadequate for ensuring protection of worker health”; or
   
• The OSHA PEL alone may be inadequate for ensuring protection of worker health, as is the case for TCE, according to EPA.

EPA states that as it moves forward with a risk management rulemaking for TCE, it will “strive for consistency with existing OSHA requirements or best industry practices when those measures would address the identified unreasonable risk.” EPA will propose occupational safety measures in the risk management process that would meet TSCA’s statutory requirement to eliminate unreasonable risk of injury to health and the environment.

Next Steps

EPA states that it is now moving forward on risk management to address the unreasonable risk EPA identified with TCE. EPA notes that while the risk evaluation included a description of the more sensitive endpoint (fetal heart malformations), EPA did not rely on it to determine whether there is unreasonable risk from TCE because of direction not to do so that was provided by the previous political leadership. EPA nevertheless identified unreasonable risks for most uses of TCE, but according to EPA, the magnitude of the risk from exposures to TCE would have been greater had EPA relied upon the fetal congenital heart defect (CHD) endpoint that had been used in previous EPA peer-reviewed assessments. Therefore, EPA developed existing chemical exposure limits based on both the immune endpoint and the CHD endpoint in support of risk management, and the public will have an opportunity to comment on these in the forthcoming proposed regulatory action.

Separately, EPA is conducting a screening-level approach to assess potential risks from the air and water pathways for several of the first 10 chemicals, including TCE. The goal of the screening approach is to evaluate the surface water, drinking water, and ambient air pathways for TCE that were excluded from the 2020 risk evaluation, and to determine if there are risks that were unaccounted for in that risk evaluation. EPA states that it expects to describe its findings regarding the chemical-specific application of this screening-level approach in its proposed risk management rule for TCE.

Additionally, EPA expects to focus its risk management action on the COUs that drive the unreasonable risk. EPA notes that it is not limited to regulating the specific activities found to drive unreasonable risk, however, and may select from among the range of risk management requirements included in TSCA Section 6(a). EPA states that as a general example, it may regulate upstream activities (e.g., processing, distribution in commerce) to address downstream activities (e.g., consumer uses) driving unreasonable risk, even if the upstream activities do not drive the unreasonable risk.

Commentary

The Acta Group (Acta^®) notes that the same legal issues we flagged with regard to EPA’s previous final revised risk determinations are common to the Final Revised Risk Determination on Trichloroethylene. See, e.g., the Commentary in our November 11, 2022, memorandum on the Final Revised Risk Determination on Methylene Chloride. We focus our discussion here on the events leading up to the Final Risk Evaluation for Trichloroethylene, that include scientific disagreements both within and external to EPA, about basing the unreasonable risk determinations on CHDs, as reported by Johnson et al. (2003).

At the start of the Biden Administration, EPA characterized the previous Administration’s decision not to rely on this study as “political interference” in science. This description fails to appreciate the legitimate differences of scientific opinion that exist on this topic. We raise this issue because it remains an active focal point from both sides of the debate as EPA moves forward with its draft risk management rule on TCE. Below, we highlight several of the scientific opinions and decisions that were made on this complex issue.

During the peer review of the Draft Risk Evaluation for Trichloroethylene, the TSCA Science Advisory Committee on Chemicals (SACC) stated the following:

Members of the Committee recognized that the results of the Dawson/Johnson experiments were obtained in one laboratory and have not been replicated in another in vivo mammalian study. Dr. Paula Johnson participated in a subsequent investigation by Fisher et al. (2001) to score slides and assure the same cardiac dissection technique was used as in the prior studies. No anomalies were found in the heart of offspring of these rats given multiple high doses of trichloroethylene, trichloroacetic acid (TCA) or dichloroacetic acid (DCA) during pregnancy. The negative findings of this oral bolus assay were supported by the GLP drinking water study by Charles River Laboratories (2019).

The SACC also stated that:

There was a lengthy discussion of the cardiac effects studies and differences of opinion expressed by Committee members concerning the adequacy of the Dawson/Johnson and the Charles Rivers studies…Some of the Committee members felt the Johnson et al. (2003) study lacked credibility and should not be relied upon by the EPA.

While the SACC questioned the credibility of the study (its results have not been reproduced in subsequent studies), it did not reject its use in the risk evaluation.

In the Final Risk Evaluation for Trichloroethylene, EPA did not rely on Johnson et al. (2003) for quantifying risks. Instead, EPA concluded under Section 3.2 “Human Health Hazards” that:

…acute immunosuppression and chronic autoimmunity were the best overall non-cancer endpoints for use in Risk Evaluation under TSCA, based on the best available science and weight of the scientific evidence, and were used as the basis of risk conclusions in Section 4.5.2. The selection of these endpoints for use in risk conclusions was supported by the SACC peer review panel [citation omitted].

The SACC supported the use of the immunotoxicity endpoints (rather than CHD) as the most appropriate for establishing the point of departure and supporting conclusions about health risk.

EPA stated in the notice for the Final Revised Risk Determination on Trichloroethylene that it:

[V]iews the peer reviewed hazard and exposure assessments and associated risk characterization [in the Final Risk Evaluation for Trichloroethylene] as robust and upholding the standards of best available science and weight of the scientific evidence per TSCA sections 26(h) and (i).

It is gratifying to see this Administration is taking a hard look at the scientific justification for its risk determinations, especially when this Administration had raised issues with the fact that the previous Administration came to the same conclusion.

In any case, EPA is including both endpoints for consideration, stating in its January 9, 2023, press release: that:

EPA developed existing chemical exposure limits based on both the immune endpoint and the CHD endpoint in support of risk management, and the public will have an opportunity to comment on [the two endpoints] in the forthcoming proposed regulatory action.

There will undoubtedly be significant interest in this issue. If the final rule is based on the CHD endpoint, the existing chemical exposure limit (ECEL) will be much lower than if the ECEL is based on the immune effects (as shown below). EPA’s conclusion of the risk evaluation representing the best available science would seem to preclude EPA basing an ECEL on CHD effect.

Comments will likely be submitted from proponents and opponents of the Johnson study on CHD. We mention this because EPA excluded the cardiac effects under Section 3.2.5.4.1 of the Final Risk Evaluation for Trichloroethylene titled “Best Overall Non-Cancer Endpoints for Risk Conclusions.” Regardless of why this exclusion was originally made, the Biden Administration approved this updated, final document, signaling its concurrence with the previous Administration and the SACC.